Aluminum-coated piston



Dec. 15, 1936. D. J. BLOCK 2,063,904

.ALUIVIIUJIVIl COATED PISTON Filed oct. 17, 1934 vPatented Dec. .15, 1936 UNITED STATES PATENT OFFICE ALUMINUM-COATED HsToN David Julian Block, Winnetka, lll.

Application 3 Claims.

in its ordinary state. It has now been discovered that a permanently bonded aluminum coating may be' produced by volatilizing aluminum, for example, in an electric arc in the absence of gases active toward aluminum and preferably in an extremely high vacuum, and then condensing the volatilized aluminum on a clean metal surface.

The invention is illustrated in the drawing, in which- Fig. 1 is a diagrammatic sectional elevation of a plating chamber and apparatus; and Fig. 2 is a longitudinal section of a coated piston head.

As illustrated in Fig. 1, an arc circuit comprising an aluminum anode i and a cathode! of aluminum, carbon, or other material, is provided in a chamber 3 adapted to be evacuated. Objects l to be coated are distributed about the 'chamber in such manner that their surfaces to be coated will be exposed to the volatilized aluminum. Other surfaces maybe covered if desired. These surfaces'should rst be carefully cleaned, and particularly grease and oil should be removed. The cleaning should, therefore, include treatment of the surfaces with a grease solvent such as gasoline or carbon tetrachloride.

After cleaning, the objects are placed in the plating chamber and a vacuum is then drawn. The drawing of a proper vacuum will ordinarily require from one-half to two hours or more, evacuation being -continued until a' vacuum of 1x10-4 millimeters or less is obtained and held. So-called scavengers or chemical means of assisting the drawing of the vacuum may be used if desired. Vaporized aluminum itself may be so used.

The arc circuit is then turned on and current maintained until .a coating of the desired thickness is formed upon the metal surfaces.4 In the case of cast iron piston heads, for which the coating is particularly valuable, the desired ocmber 17, 1934, serial No. 748,741

(ci. sos- 14) thickness is of the order of 1 to 4/-1000th of an inch. Other readily oxidizable metals such as magnesium, and other readily volatilizable metals may be plated in the same manner. This method of 5 coating appears to be the only practical known method for coating with magnesium. Cast iron piston heads 5 coated in the above manner with a layer of aluminum 6 appear to be considerably superior to c ast iron piston heads or 10 aluminum piston heads in service.

Piston heads have also been plated with both magnesium and aluminumby this process.

Other surfaces adapted to be exposed t'o internal combustion engine explosions suchA as 15 cylinder walls or heads likewise appear to be particularly beneiited by coating with aluminum, magnesium, or other readily oxidizable metal of this type.

. given for clearness of understanding only, and

no unnecessary limitations should be understood therefrom, but the appended claims should 30 be construed as broadly as permissible, in View of the prior art.

What I regard as new and desire to secure by' 'Letters Patent1s: 1. A ferrous base piston for internal combustion engines having integrally bonded on the head thereof a layer of metal of the class consisting of aluminum and magnesium and mixtures thereof, said coating having been condensedl upon saidhead in an 4inert atmosphere, and hav- 40 ing a thickness of the order of .001 to .004 inch.

2. A piston as set forth inclaim 1 in which the metal is aluminum.

3. A piston as set forth in claim 1 in which the1 metal ismagnesium.

DAVID JULIAN BLOCK. 

